The vortex tube, also known as the Ranque-Hilsch vortex tube, is a device that separates a compressed gas into hot and cold streams. It has no moving parts. Pressurized gas (usually air) is injected tangentially into a swirl chamber and accelerates to a high rate of rotation within an extended tube. As the rotating gas travels along the tube, it separates into a relatively warm outer shell and a cool core. The outer shell of the compressed gas can be allowed to escape from the end of the tube through an annular opening. The remainder of the gas can be forced to return in an inner vortex of reduced diameter within the outer vortex. The rotation rate (angular velocity) of the inner gas is the same as that of the outer gas, resulting in a “solid body rotation” of the gas. The solid body rotation is thought to be due to the relatively long time in which each parcel of air remains in the vortex. This allows friction between the inner parcels and outer parcels of gas to have a notable effect. For this effect to occur, the swirl chamber must be suitably dimensioned, for example to be sufficiently long for the solid body rotation and separation to occur.
Vortex tube-operated enclosure coolers, which are known in the art, have been developed to maintain a cool environment within relatively small enclosures such as electrical enclosures and control panels by producing a refrigerated air stream directed into the enclosure. Systems for electronics enclosures can be required to meet various industry standards, including NEMA standards.
NEMA ratings are standards that are useful in defining the types of environments in which an electrical enclosure can be used. The NEMA rating system is defined by the National Electrical Manufacturer Association (NEMA), and frequently signifies a fixed enclosure's ability to withstand certain environmental conditions.
NEMA ratings are mainly applied to fixed enclosures. For example, a NEMA rating would be applied to a fixed electrical box mounted outside, or a fixed enclosure used to house a wireless access point. Most enclosures rated for use in environments where the enclosure is subjected to spraying of water or cleaning have a NEMA type 4 rating. NEMA ratings have more stringent testing requirements to verify protection from external ice, corrosive materials, oil immersion, dust, water, etc.
The NEMA type 12 rating indicates that a given enclosure is rated appropriately for indoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment, to provide a degree of protection against dirt, circulating dust, lint, fibers, and other airborne particles and against dripping and light splashing of liquids.
The NEMA type 4 rating indicates that the enclosure is rated for either indoor or outdoor use to provide a degree of protection to personnel against incidental contact with the enclosed equipment, to provide a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water, and hose-directed water. The NEMA type 4 rating also indicates that the enclosure will be undamaged by the external formation of ice on the enclosure.
The NEMA type 4X rating indicates that the enclosure is rated for harsh corrosive conditions as well as the conditions specified for NEMA type 4 above.
It has proven to be difficult to provide a vortex tube cooling apparatus suitable for cooling electronics enclosures that meets the more rigorous NEMA standards. As well, prior art cooling systems suffer other disadvantages. One drawback of known systems stems from the difficulty inherent in a system that permits a flow of external air through an enclosure that may contain sensitive components. As well, when a conventional vortex tube is used, it can provide an opening into the enclosure that permits moisture or other unwanted substances to enter. Further, conventional vortex tubes tend to be larger so that openings are oriented away from possible sources of contaminants.